The new chief executive at Trinity Mirror Simon Fox has quickly stamped his authority on the newspaper group, announcing a major shake-up and expressing astonishment at the poor state of its digital operations.

After five weeks in the job, the former HMV chief has merged Trinity's national and regional newspaper divisions into a single unit, a strategy he called "One Trinity Mirror". "It was very obvious coming in as an outsider that it was not an efficient structure," he said. "We weren't presenting a joined-up approach to our advertisers."

Asked if this meant a break-up and sell-off of the regionals was off the agenda, Mr Fox said: "We think we're stronger as one unit, rather than several units." He added: "It doesn't mean we're not divisible in the future."

Mark Hollinshead, the head of the national titles, is promoted to a new role of chief operating officer. He will oversee all the papers, which range from nationals such as the Daily Mirror to about 130 regionals.

Mr Fox said it was "too early to say" how many jobs will be lost, although "there will be some opportunity for efficiency".

Georgina Harvey, the regionals boss, and Nick Fullagar, the long-serving PR man, who dates back to the days of the disgraced ex-owner Robert Maxwell, will go.

Mr Fox, who has little newspaper experience apart from as a non-executive director of Guardian Media Group, said "it hasn't been a huge culture shock" since he joined. But in a swipe at his predecessor, Sly Bailey, Mr Fox was scathing about how the group has "neglected the digital development of our core brands".